Record changer for talking machines



May 16, 1961 Filed Nov. 27, 1957 F. CAVALLO FAL RECORD CHANGER FORTALKING MACHINES 2 Sheets-Sheet 1 May 16, 1961 F. cAvALLo ETAL 2,984,491

RECORD CHANGER FOR TALKING MACHINES Filed Nov. 27, 1957 2 Sheets-Sheet 2/0 N 4 a f 4 3 E E L 4 E A E E @J United States Patent 2,984,491 RECORDCHANGER FOR TALKING MACHINES Friedrich Cavallo, Meybachufer 8,Berliu-Neukolln, Germany, and Hellmuth Georg Martin Petzhold,Blucherstrasse 40, Berlin, Germany Filed Nov. 27, 1957, Ser. No. 699,243Claims priority, application Germany Dec. 1, 1956 14 Claims. (Cl.274-10) This invention relates to a record-changer in which a stack ofdisc records,` each provided with a large central hole, is arranged upona stack mandrel or spindle which revolves during the playing of a recordand in which the stack can be divided from time to time, by grippermembers mounted in the interior of the stack spindle, at the place` ofthe record to be played, and it is primarily concerned with the improvedsupporting of the stack spindle and of the operative elements lodgedtherein in the foundation of the apparatus.

A known constructional form of a record-changer of this nature disclosesa vertical hollow spindle for the records, carried by superposed spacinggripper rings, which is rotatably supported in two rings of balls in asocket ring standing upon a mounting plate, and is driven through rubberwheels and a driving plate secured to it In seeking the selected recordthe gripper members are displaced vertically by the aid of a liftingspindle ascending in the interior of the hollow stack spindle until thedisc-seeker, moving synchronously therewith, has found the appropriaterecord. They then engage, with their tongues protruded at this moment bya control rod, through longitudinal slots in the hollow stack spindle,into the spacing gripper ring of this record, and raise this recordfarther and the part of the stack of records located above it, for thepurpose of forming a working gap for the tone arm, whereupon the tonearm is swung into this working gap, and at the same time the hollowstack spindle, and all the records located upon it, are set in rotation.The weight of the partial stack of records lifted is here carried,through the medium of the gripper members, by the aforementionednon-rotating control rod. Between the control rod and the gripperarrangement, multiple ball bearings are fitted at the requisitepositions.

Although the kinematic construction of this known arrangement thusappears to be satisfactory, it does not yield tonally pure and noiselessreproduction of records. The object of the present invention is toremedy this defect. According to the invention this problem isfundamentally solved by the fact that the bearings for the stackspindle, and the adjusting and supporting members arranged therein andacting upon the stack of records, are constructed in a particularlyadvantageous manner.

The invention therefore relates to a record-changer with a stack ofrecords arranged upon a rotating vertical stack spindle and divisible atthe place of the record to be played, wherein the stack spindle isrotatably supported in a socket secured fast to the casing, and can bedriven by means of a friction wheel, the record-gripper members can betaken along by a lifting spindle, which, by an adjusting nut mounted inthe socket, is vertically displaceable in the interior of the stackspindle, and, with the aid of a spring-loaded control rod, which isvertically displaceable in the interior of the lifting spindle by meansof a control cam xed to the casing, are displaceable radially outwardsthrough longitudinal slots in 2,984,491 Patented May i6, 1961 the stackspindle for the purpose of gripping a record disc, and the recordgripped by the gripper members, together with the records located aboveit in the stack, is additionally displaceable vertically with the helpof the control rod for the purpose of temporarily forming a working gapfor the tone arm to be swung in and out relatively to this gap.

According to the invention, the stack spindle is rotatably supported, inthe socket secured fast to the casing, by means of a ball bearing whichcomprises only a single ring of balls arranged in a plane perpendicularto the axis of the stack spindle, and at least one race ring is dividedin this plane.

The invention is based. upon the following inventive considerations anddiscoveries: in playing a record, its speed, and therefore that of thestack spindle carrying it, must be absolutely constant, since the humanear detects even the slightest fluctuations in speed as unendurabledistortions of pitch, namely the so-called howling Apart from theconditions in the actual. drive, namely in the motor, or intoothed-wheel or friction-wheel gears, the speed of revolution ismaterially dependent upon the quality of the bearing supporting thestack spindle. This supporting is diicult in record-changers, owing tothe fact that in consequence of the general construction of the devicethe bearing circles must have an unusually large radius, and thereforealready exhibit in themselves a greater frictional resistance thanordinary small bearings.

The maintenance of a constant speed of revolution is in the present caserendered still more diliicult by the fact that no reserve power can beprovided in the drive: for on grounds of economy a friction-wheel gearmust be employed the transmission members of which consisting forinstance of rubber, are not suiiciently rigid in form to be able totransmit relatively great driving forces without deformation, and thefluctuations in speed conditioned thereby. With the weak driving forcesthat are permissible, however, even the slightest fluctuations in thebearing friction give rise to such disturbing fluctuations in speed.Owing to the necessarily large size of bearing, the use of journalbearings is precluded, because rwith the large bearing surfaces eventrifling variations in the lrn of lubricant, or differences oftemperature, cause unavoidable fluctuations in speed. Even theaforementioned kno-wn stack-spindle bearing, however, with the aid oftwo rows of ball bearings, is imperfect. The stack spindle bearing isstressed both by axial forces and by radial forces. The axial forcesarise from the weight of the stack of records and the intrinsic weight of the stack-spindle and its internal organs, while the radial forces arebrought about by the application pressure of the friction drive and bycentrifugal forces owing to the unavoidably eccentric position of thestack-spindle aggregate as a whole. A further disadvantage of ballbearings of the usual construction as compared with plain bearingsconsists in the considerable bearing noise, `which has a particularlydisadvantageous effect upon the reproduction of the record when itoccurs unevenly. In such bearings, with two rows of balls, with meanssuch as alone come into question for the economical manufacture of amass production article such as a recordehanger, not even uniformity canbe attained, let alone a sufficient reduction of the bearing noise. Insuch bearings lwith two rows of balls one row must be constructed as afixed bearing, and the other, owing to dierences of temperature, as aloose bearing, the tting of which is critical. if the loose bearing istoo rmly seated, the small driving forces provided do not suffice forthe correct adjustment of the balls, and the result is ball noise, onaccount of partly fluttering and partly jamming balls. If the loosebearing is too loosely seated, on the other e? hand,.there is the riskthat allthe b alls may give rise to fluttering noises.

These disadvantages `of a two-row ball bearing are entirely eliminated,or at least reduced to a'practically immaterial trace, in .the bearing'according tothepresent invention; By employing only a single -row 'ofballs yinstead ofy two rows, the ball noise in itself is alreadysubstantially reduced, and the running irregularities in the loosebearing member of the known two-row ball bearing are also absent. Theretherefore remains, in the bearing according tothe present invention onlyquite a slight and also uniform bearing noise, which does not disturbthe reproduction of records.

For the purpose of satisfactorily taking" upgdboth the radial and theaxial forces, the Vbearing isconstructed as a divided double-shoulderbearing in which at least one race is divided in the running pla'neofthe row of balls. On the lines of this invention, therefore, eitherthe inner or the outer race ring'or both; must bezdivided in thismanner. In consequence of this axial' division the axial ball clearanceor set ofballs'rnay primarily be kept as small as may be desired,which/-results'in a corresponding automatic reduction' in the size ofthe radialV ball clearance or set of balls. Consequently this novelbearing can be economically manufactured with great exactitude.

In the sense of this invention, moreover, the lifting spindle lodged inthe hollow stack spindle, and not rotating but only axiallydisplaceable, with which the recordgripper is adjusted to the desiredstack-separating plane, can be supported in a particularly reliablemanner.

The special construction of a record-changer with record discs arrangedone above another upon a stackspindle, has the result that this liftingspindle has a disproportionately great free length above its adjustingnut, and therefore executes where possible, with incorrect mounting ofthe adjusting nut, inadmissibly large swaying movements with its head.

The mounting of the lifting spindle is eifected at two places, namely onthe one hand at the lower end in a slideway, and on the other hand,further up, in the thread of the adjusting nut. Since not only therecordgripper but also the tone arm are brought to the correct playingheight by the lifting spindle, the tone arm is secured to the spindleunderneath theA adjusting nut, and exerts upon the adjusting nutbearing, owing to its eccentric arrangement, considerable radial andaxial forces.

In the case of the known record-changer already mentioned, the adjustingnut is mounted in a plain bearing, and is rotatably supported upon anaxial pin of a ring socket and axially clamped between the ring socketand the 'fixed foundation plate supporting the ring. It is found byexperience that this mounting does not work without disturbance. On theVbasis of inventive considerations the cause of disturbance has beenrecognised to be that the wide manufacturing allowances that arenecessary for mass production in stamping the mounting plate, and in themass formation of the holes and screw threads for the socket supportsand so forth, are liable to be additive in an incalculable manner, sothat a steady mounting of the lifting spindle is not ensured, andfurthermore the remaining bearings in the socket, particularly thesensitive stack-spindle bearing previously discussed, are injuriouslystressed.

In order to obviate these disadvantages of the known arrangement withoutgiving up the requisite wide manufacturing allowances, according to afurther development of the invention, the adjusting nut for the liftingspindle of the record-gripper and of the tone arm is supported in asingle bearing, which is carried by the socket that also carries thestack-spindle bearing. This adjusting-nut bearing preferably consists ofa two-row bearing, whereinvthe two rows of ,balls are resilientlyclamped to one another in an axial direction. The rows of balls mayAlhowever alternatiyely be. rigidly clamped .together by means of, a nut.Byn this mountingiof the adjusting nut on a single structural member,the surfaces of which that are important for supporting purposes can bemanufactured by rotary machining of the highest accuracy, and in aprecision ball bearirlgnaA steady supporting of the lifting spindle isensuredV without special manufacturing expenditure.

The invention also concerns itself, within the scope kof the fundamentalproblem of the tonallypure reproduction of records, with the supportingof the controlrod by which the record-gripper members are shiftedradially outwards at the position of the selected record through thelongitudinal slots in the stack-spindle,k for the purpose of graspingthis record. This control rod, during the playing of a record, carriesthe weight of the lifted partial stack of revolving records. In theknown record-changer previously mentioned, the control rod does notyparticipat'e'in'the rotation Vof the record, anda ball bearing isarranged between it and the record-gripper. For this ball bearing,however, the same considerations apply which were put forward furtherback for the stack-spindle' supporting bearing, and it is found byyexperience that' thisball bearing does in fact form likewise, at thehead of the control rod, a'source of disturbance leading totonalrfluctuations. Since, as mentioned previously, the rotationaldriving forces available are but small, there is not the possibility ofreplacing the disturbing ball bearing on the head of the control rod byan equivalent plain bearing.

As compared with this known arrangement, the recordchangerM according tothe present invention is characterizedy by thefeature that the controlrod' supporting the raised partial stack of records' for the'record-gripper members consists of two ends, the lower one of which, avery short end, bears non-rotatably on the control cam mounted ixedly on'the casing, While the very long upper end, with kthe -aid of a one-balljournal bearing, is mounted in `the lower end, and participates in therotation of the stack of records. This constructional alteration, ascompared with the known arrangement, involves not merely a simpleexchange of a ball bearing for a different type of bearing, but yields,within the framework of the present problem, a decisive improvement. Thecontrol rod, like the lifting spindle, constitutes -a long bar membersupported at one end, with a working surface located at the free end,and therefore has a tendency to execute swaying movements. In the knownconstructional form, with a ball bearing arranged at the head of thecontro-l rod, this is subjected, on account of the great leverage, tocomparatively large radial loads, and therefore tends towards irregularrevolution, leading to disturbances in reproduction. With the formationof the control rod according to this invention, however, any existingradialforces have practically no effect at all on the journal bearing,because this bearing is located close to the rocking point of anyswaying. The axial loads occurring inthe journal bearing are practicallywithout effect, since they are taken up by the carrying ball withoutnoise and practically without resistance to rotation.

Finally, the invention is also `concerned with the elimination of afurther source of disturbance -located in the interior of thestack-spindle. This consists, as inventive investigations andconsiderations have shown, in possible frictional contact between thecontrol rod and the stressing spring pressing it against the controlcam. Since this stressing spring, constructed as a spiral spring, iseffective only during the period of operation, in which the control rodhas urged the record-gripper members outwards, and brings the upperrecord stack, thereby divided ci to tonearm working distance from thelower record stack, and thus carries it, it is supported on the liftingspindle, and therefore does not participate any morethan the latter inthe rotation of the stack-spindle, theV record-gripper members and thecontrol spindle. A rotary `bearing must therefore be arranged betweenthe non-rotating stressing spring and .the rotating `part of the controlrod. According to the invention this rotary bearing consists of theorementioned journal bearing between the two sections of the controlrod, in that the stressing spring is supported with its upper end on thenon-rotatable lifting spindle land with its lower end on the likewisenon-rotatable under portion of the control rod. Now however there isalso the risk that the stressing spring, owing to the forces occurringduring operative compression, may lose its cylindrical form, may deviatelaterally with a part of its coil right into the region of the controlrod, and check the latter in its rotation. In order to preclude thisjamming, which would lead to disturbances in reproduction in a furtherdevelopment of the invention, between the stressing spring and thecontrol rod is arranged an intermediate sleeve which is supported inthecorrect position, preferably by means of a flange, at the non-rotatablelower end of the control rod.

The constructional example hereinafter more fully described, andillustrated in the accompanying drawings, is intended to explain theinvention more fully, but not to restrict it.

Figure l shows a diagrammatic front view of a recordchanger withrecord-preselecting means, in which the invention is incorporated;

Figure 2 shows a partial longitudinal section through the stack-spindle,with associated constructional and operational parts;

Figure 3 shows a diagrammatic longitudinal section of one constructionalform of the stack-spindle bearing;

Figure 4 shows a diagrammatic longitudinal section through another formof construction of a stack-spindle bearing;

Figure 5 shows a diagrammatic longitudinal section through yet anotherconstructional form of a stack-spindle bearing; and

Figure 6 shows on a lower part of Figure 2.

Since the invention is concerned essentially with the construction of arecord-changing means, only those parts of a disc-record reproducingapparatus are shown in the general view of Figure l which are requisitefor the elucidation and comprehension of the invention.

The apparatus represented in Figure 1 comprises an instrument frame,consisting of two mounting plates 1 and 2 and two pairs of supportingcolumns 3 and 4, the latter ofwhich are connected with one another by ahead plate 5. To the pair of columns 3 is secured a selector register 6of ya record-preselecting device of the usual construction, which isactuated by a diagrammatically represented selecting head 7,electro-magnetic for example, in a manner known in itself. The otherpair of columns 4 serves as a guide for the vertically adjustable tonearm 8, which can be swung in and out, Iand the swinging members of which-are denoted generally by 9.

On the under side of the motor board or upper mounting plate 1 issecured the main driving motor 10, which, by way of a diagrammaticallyindicated gear train -11 which can be engaged and disengaged, drives anadjusting nut 12 for a square-threaded hollow lifting spindle 13, Thislifting spindle 13 supports with its head portion 14 (Figure 2) therecord gripper members, which will be hereinafter described inconnection with Figure 2, and carries in the lower region a sensingorgan V15 for the selector register 6 of the record-preselecting device.The sensing organ 15 is connected, by a diagrammatically representedconnecting member 16, with a tone-arm lifting column 17 for jointup-and-down-movement, and furthermore, in a manner not illustrated, isso constructed that it` is normally urged towards the selector register6, but after striking against that selector-register slide which isprotruded to correspond to the selected record it deviates for a shorttime, urges the slide back again into the normal position, and at thesame time, through electrical switching means, disconnects the train ofgears I11, so that the lifting spindle 12 and the tone arm 8 remainstationary at larger scale a partialview of the the levei of theselected record in the stack of records to be hereinafter described.After the record has been played, the lifting spindle is set in motionagain by mechanical and electrical controlling means not furtherillustrated.

'Ihe record motor 18 carried by the mounting plate 1 drives theturntable 19 through a friction wheel 19', and also the stack-spindle 20rigidly connected therewith for the record-stack 21u, 21.

In the interior of the lifting spindle 13 is arranged a control rod 22,which bears with its foot. upon a control lever 23. This control lever23 is fulcrumed on the lifting spindle 13, Vand is so actuated, by gearand cam elements 24 diagrammatically indicated, that it moves thecontrol rod 22 up and down within the lifting spindle in the workingrhythm, for purposes known in themselves, to be hereinafter more fullyexplained.

The construction of the stack-spindle of the recordchanger, in which theinvention is embodied, will now be described in detail with reference toFigure 2.

On the upper mounting plate 1, by means of short columns 25, a socket 26is secured, the bores and working surfaces of which are very accuratelymachined. The socket 26 has a wide central bore, with a downwardlyextending sleeve extension 27. The external periphery of this sleeveforms the inner bushing of a two-row ball bearing 2S, the outer bushingof which is according to the invention made in two parts, and is formedin the upper part by a sprocket wheel 29 and in the lower part by anadjusting nut 30 for the lifting spindle 13. The chain wheel 29, drivenby the main motor 10 in a manner previously described is keyed in anaxially displaceable manner to the adjusting nut 30 at 29', and the twoparts 27 and 30 are pressed against one another by a spring 30', in theregion of the balls.

. In the interior of the sleeve 27 is arranged a one-row ball bearing31, the outer bushing 32 (Fig. 3) of which is made in one part and itsinner bushing in two parts 33 and 33". On the lines of this invention itis however also possible, according to Figure 4, to divide the outerbearing bush into two parts 132 and 132 instead of the inner bearingbush 133. A further constructional possibility is shown in Figure 5.Here, in the case of the bearing 231, both the inner bearing bush (233and 233) and the outer bearing bush (232 and 2.32") are made in twoparts. The two parts of the divided bearing bush are pressed against oneanother, in the example illustrated, by a compression spring 34 (Figure21). The bearing 31 carries the stack-spindle 2t), with the turntable 19secured to it at 20'. The stack-spindle 20 is constructed as a sleevesurrounding the lifting spindle 13. In a manner known in itself, it isprovided with longitudinal slots 36 corresponding in number andarrangement to the record-gripper members 35. Upon the stack-spindle 20are threaded carrier rings 37 of the usual construction for the recorddiscs 21 (Figure 1). A longitudinal rib 37' on the stack-spindle thenengages in a radial groove in each carrier ring 37, and ensures therotation of the records.

The record-gripper system arranged in the interior of the stack-spindle20 is of the usual construction. A hollow carrier body 33, whichnormally rests with its foot plate 39 upon the head member 14 of thelifting spindle 13, serves as a horizontal sliding bearing for thesliderlike record-gripper members 35, which are normally urged by atorsion spring 40 into their retracted position within the externalperiphery of the stack-spindle.

In the interior of the hollow lifting spindle 13 is arranged theaforementioned control rod 22. It consists, as will be gathered moreparticularly from the large-scale partial view in :Figure 6, of the verylong actual upper end of the rod and the short lower end 41, which isconstructed as a thrust bearing, with a bottom ball 42 for the lower endof the rod 22 and an end flange 43. The con` trol rod 22 has in itsupper section a collar 44 (Fig. 2).

assaggi and an inclined control surface 45. The axial arrangement ofthecollar 44 and the control surface 45 relatively to oneanother and to thehead member V14. of the lifting spindle l'is made such that during theupward travel of the control rod 22 inside the lifting spindle, iirstthe inclined surface 45 ,becomes operative and allows the record-gripperslider 35 to extend through the stackspindle slots 36 into therecord-carrying or turntable ring 37, and only then does the collar 44bear on the foot plate 39 ot the record-gripper carrier 3S, andsubsequently raise the record-gripper system 35, 37, 38, 4t) and theupper part Zio (Figure l) of the stack of records, which contains therecord seized by the gripper sliders 35 as the lowest one, through theheight of the tone-arm working gab (Figure l).

In Figure 2 is represented the condition in which the collar 44 justtouches the foot-plate 39 of the recordgripper carrier 33, and Figure lshows the device with l the working gap opened. After the record hasbeen played, the control rod 22 is lowered again, whereby iirst thestack of records is re-united, and then the gripper sliders 3S arereleased, and these then set free, under the inuence of the torsionspring 4t), the record previously selected. The stack of records isthereby made ready again for the next selecting and playing operation.

As will readily be gathered more particularly from Figure 6, between theend ange 43 of the lower end 41 of the control rod 22 and an innercollar 46 of the lifting spindle 13 is clamped a helical compressionspring 47, which, during the upward stroke, hereinbetore described, ofthe control rod 22, is further compressed. Between the helical spring 47and the ends 2,2y and il of the control rod is arranged a sleeve 48 withan end flange 49, which is designed to prevent, in a manner previouslyindicated according to the invention, any disturbing contact f betweenthe two operative elements.

The advantages attained by the form of construction hereinbeforedescribed in detail are set forth and explained in detail in a previouspassage.

It will be obvious from the foregoing statements, to any technologist,that the invention, with respect to its applicability and itsusefulness, is not restricted to the constructional form illustrated,but is also of advantage in conjunction with other types of disc-recordapparatus, in which the supporting by operative elements participatingin the rotation of the turntable may lead to disturbances in thereproduction of sound.

What we claim is:

l. A record handling mechanism for apertured disctype records comprisinga power source, a vertical spindle for accommodating said records, saidspindle being coupled to said source for being rotated, and a ballbearing supporting the spindle for rotation; said bearing including tworaces and no more than one group of coplanar balls between the races, atleast one of said races cornprising two sections abutting in the planeof the balls.

2. A mechanism is claimed in claim l, wherein the spindle issubstantially vertical, comprising means supporting the bearing andthereby said spindle in iixed vertical position.

3. A mechanism as claimed in claim l, wherein the spindle issubstantially vertical and is adapted to support a stack of superposedrecords, the spindle further defining at least one axial slot, saidmechanism further comprising iirst means slidable within the spindle ina vertical direction, second means coupled to said iirst means tocontrol the vertical displacement of the latter, an engaging member onsaid first means and extending through said slot to engage the stack ofrecords in accordance with said vertical displacement, and control meanscoupled to said engaging member to control the extending of the engagingmember through said slot and thereby the engaging of said stack.

l4. A mechanisinas claimed in claim 3, comprisinga threadedportion onthe iirst means, and athreaded memberengaging saidlthreaded portion andcoupled to said power sourcefor thegvertical displacement of the iirstmeans. v

A5. A mechanism as claimed in claim 4, wherein said threaded memberincludes a portion constituting a race for a further ball bearing,`comprising a support supporting the lirst said bearing and including aportion constituting a further race for said further bearing, and agroupof balls between the races o said 'further bearing to complete theklatter.

6. Ammecha'n'ism asclaimed in claim 5 comprising a sprocket Vwheel onthe threaded member coupling the latter to said power source. l

7. A mechanism as claimed in claim 5 comprising a spring urging theraces of the further bearing together.

8. A mechanism as claimed in claim l, wherein the spindle is hollow. anddefines at least one axial slot, comprising a hollow tube displaceablewithin the spindle, a carrier body resting atop said tube, a roddisplaceable within the tube to lift the carrier body therefrom, and arecord engaging member on the ,carrier body and extending .through theslot to lift a portion of the records in accordance with thedisplacement of the hollow tube.

9. A mechanism as claimed in claim S, wherein the engaging member isdisplaceable on said carrier body, comprising a spring coupled to theengaging member to urge the latter into a retracted position withrespect to said slot, said rod engaging said engaging member to urge thelatter outwardly of the slot by overcoming the action of the spring.

llt-A` mechanism as claimed in claim 9 whereinthe rod is'extendiblethrough said carrier body and includes a first portion for engaging saidengaging member and a second portion for engaging the carrier body, saidlirst and second portions being spaced so that the engaging member andcarrier body are engaged in sequence.

11. A mechanism as claimed in claim 9 comprising an end thrust bearingsupporting said rod in said hollow tube.

l2. Apparatus for selectively elevating a portion of a vertical stack ofcentrally perforated records with respect to the remainder of said stackcomprising a rotatable hollow spindle adapted to extend through therecords or said stack and deiining a lateral opening, irst means atleast in part in said spindle and vertically and radially displaceablewith respect to the spindle for selectively engaging the stack, andsecond means coupled to the first means to displace the same verticallyand radially for selecting and elevating said portion.

13. Apparatus as claimed in claim l2 wherein the iirst means comprises ahollow tube within and rotatable with the spindle, a carrier bodyresting on said tube, a record engaging member displaceable on thecarrier body radially with respect to the spindle, and resilient meansurging the engaging member to a radially innermost position whereatengagement with the stack is avoided.

14. Apparatus as claimed in claim 13 where said record means comprises arod displaceable in the hollow tube for sequentially engaging saidengaging member and carrier body for respectively urging the engagingmember radially outward and lifting the carrier body from said hollowtube.

References Cited in the file of this patent UNITED STATES PATENTS2,017,898 Gares oct. 22, 1935 2,132,993 Mitchell Oct. 1l, 1938 2,759,243Smith Aug. 2l, 1956 2,761,686 Stalling Sept. 4, .1956

